Dies for a board or film extrusion of plastic and other plasticizable and hardenable materials are known per se. The material is conventionally first heated and pressed in the plastic state through the die between a die bottom part and a die top part, in order, after a cooling and hardening phase, to obtain a board which conforms as exactly as possible to stipulated dimensions.
It is also known, for example from U.S. Pat. No. 4,454,084 or German Patent Publication No. DE 198 55 751 A1, that the thickness of the die, that is to say the distance between a die bottom part and a die top part, may be finely set before extrusion, in order to adhere to stipulated thickness tolerances.
Furthermore, the processing of plastic boards by thermo forming is known, in which thermoplastics are conventionally formed in the heated state, for example, deep-drawn in a vacuum.